Whey (milk serum) is a by-product of manufacturing cheese or the like, and has conventionally been discarded as waste.
In recent years, effective ways of using this by-product have been investigated, and as well as being used as a raw material for whey protein or lactose, whey is also being used as a flavor improver in bread and cakes, a raw material for beverages, and a raw material for milk formula for infants.
However, whey has poor thermal stability, and when heating is performed for pasteurization purposes or the like, precipitation or gelling tends to occur due to aggregation and the like of the whey protein contained within the whey. Accordingly, in order to ensure no denaturation of the whey protein, pasteurization treatments for whey or products containing whey as a raw material must be conducted using a low temperature long time pasteurization method (LTLT) or a high temperature short time pasteurization method (HTST), for example by heating within a range from approximately 63° C. for 30 minutes through to 72° C. for 15 seconds, and therefore applications for whey have been limited.
Dairy products hold great promise as a good source of calcium, and whey is no exception. However, as described above, whey suffers from the problem of having low thermal stability. In particular, if a calcium-containing compound is added to whey to increase the calcium content, with the aim of enhancing the usability of the product as a calcium source, then the thermal stability deteriorates even further.
If the calcium is removed from whey, then although the thermal stability improves, the calcium content falls below that of the raw material whey, and therefore its usability as a calcium source is lost.
In response to these types of problems, a variety of investigations have been conducted with the aim of improving the thermal stability of whey.
For example, Patent Document 1 discloses a method for manufacturing a modified whey product which has excellent thermal stability, and retains good thermal stability even when the calcium content is increased, the method including a calcium reduction step of reducing the calcium content of a raw material whey liquid to obtain a calcium-reduced whey liquid having a calcium content of not more than 313 mg/100 g of solids and a protein content of not more than 21 g/100 g of solids, and a heat treatment step of heat treating the calcium-reduced whey liquid under conditions of 80 to 150° C. for a period of 30 minutes to 1 second. The reduction of the calcium content in the raw material whey liquid is performed by a cation exchange treatment.
Patent Document 2 discloses a method of obtaining a fermented whey preparation by subjecting an aqueous solution of whey protein prepared with a solid content concentration of 11 to 35% by weight and a pH of 6.5 to 8.0 to high-temperature pasteurization, followed by lactic acid fermentation and then homogenization of the obtained fermented liquid, wherein the lactose contained in the aqueous solution of whey protein after the high-temperature pasteurization is enzymatically degraded by lactase before the lactic acid fermentation, during the lactic acid fermentation and/or after the lactic acid fermentation, thereby enhancing the sweet taste.